This invention relates to solar heating apparatus, and particularly to the collector and the heat transfer elements employed therein.
The prior art contains many proposals for utilizing insolation for heating buildings, especially homes. All of these systems include a collector which is exposed to incident solar radiation and contains a heat exchange device which transfers absorbed energy to a circulating fluid medium. That medium may be a gas (e.g. air) or a liquid (e.g. water), and the warm circulating stream may be used immediately for heating purposes, or its heat content may be transferred to a storage device and utilized later.
Known collectors are characterized by various disadvantages which have limited the utility of solar heating systems. For example, some sollectors, particularly those which utilize a liquid heat exchange medium, are quite expensive and require considerable maintenance. Others exhibit low efficiency. This is manifested by the large size of the unit and may be attributable to the relatively small area of the heat exchange surfaces, or to inefficient transfer of heat to the circulating medium, or to a combination of these and other factors. Finally, many collectors must be mounted in an inclined position, and thus are inconvenient to use and consume considerable space.
One of the main objects of the present invention is to provide an improved collector for a solar heating system which is economical to construct and install, requires little maintenance and affords good efficiency. According to the invention, the new collector utilizes a gaseous heat exchange medium and is characterized in that it employs a group of heat exchange units which are relatively inexpensive and afford an unusually large heat exchange area. Each of these heat exchange units comprises a pair of open top metal foil pans having flat bottom walls, which abut one another, and outwardly flaring conical side walls, and carrying a black energy-absorbing coating. The collector comprises a glazed, insulated box, preferably of rectangular shape, having a chamber between the glazing and the back wall which is filled by a layer of the heat exchange units. These units are stacked in interfitting relationship in rows and columns, with the axes of adjacent interfitted units in each row and in each column extending in mutually perpendicular directions. The box is ported so that a working fluid, such as air, may be circulated through the array of pan units in the chamber.
The pans employed in the heat exchange units preferably are of the same type and size as those used heretofore as containers for frozen meat pies. However, the mating flat bottoms of the pans of each unit should be provided with registering openings so that the circulating gas will be able to flow through, and not just around, the layer of heat exchange units.
The preferred collector affords a heat transfer area on the order of 14 square feet per square foot of glazing and inherently provides for effective heat exchange contact between the circulating gas and the pan units. Therefore, the collector can be relatively small. Moreover, because of the shape and arrangement of the heat exchange units, the collector operates most efficiently when in the vertical position. Thus, the invention makes possible mounting on a side wall of a home or building, and thereby facilitates installation and conserves space.
Although the improved collector may be employed in various types of heating systems, some of which have heat storage capability, the presently preferred embodiment combines the collector with a fan unit which is adapted to be mounted in a standard window. This embodiment constitutes a portable, auxiliary room heater which can handle the heating requirements for a room of average size when the sun is shining, and thus permits a homeowner to derive immediate benefit from solar heating for a relatively modest expense.